Toolholder for circular thread forming tools



Sept. 111 W R. ROSSETT] 2,523,45fi

TOOLHOLDER FOR CIRCULAR THREAD FORMING TOOLS Filed Dec. 26%394 5 3 Sheets-Sheet l BY MW apt, 26, 195G R. ROSSETTI TOOLHOLDER FOR CIRCULAR THREAD FORMING TOOLS Filed Dec. 26, 1945 3 Sheets-Sheet 2 I71 veh Rev-re Rossetti.

54am. 2%, 1950 R. ROSSETTH TOOLHOLDER FOR CIRCULAR THREADFORMING TOOLS 3 Sheets-Sheet 3 Filed Dec. 26 1945 59 llllllllll lllllllll .Z'wverzf r, Fewe Haasefli )2 ya I Atfy Patented Sept. 26, 1950 TOOLHOLDER FOR CIRCULAR THREAD FORMINGTOOLS Iten Rossetti, Geneva, Switzerland I Application December 26, 1945, Serial No. 637,271

In Switzerland December 27, 1944 3 Olaims. (-01. 1 -104) '1 Itis well known that-in order to cuta screw thread with a forming tool on a lathe, it is necessary to set the cutting face of the tool at-a predetermined angle with respect to a plane perpendicular-tothe axis-of the screw. This angle is determined by the slope of the thread with respect to. said-plane, i. e. bythe =d-iameter andthe pitch of the middle helix of the thread to be produced. According-to actual practice, it is necessary to go through a trying process, tofind the most favouring the angleoi tilt of 'the tool'with respect to a plane perpendicular to the axis ofthe thread to be formed. This device'carriesindicating-means consisting ofanindex and a graduated scale capable of displacements one with respectto the othen. Displacement transmitting members are providedbetween ,saidindicating means and said tool causing a widespread of the graduations as compared with the'angular displacements per- .formed by the tool during its adjustment, Clamping means areprovided permitting the tool to be securely fastened in said tool-holder in the adjusted position.

Another objectofthe invention is-a tool-holder in which the displacement'transmittlng members consist in a finger slidable in a slot provided in a stationary part and a groove cut in a part moving with the tool, said slot and groove forming a small angle.

A further objectof the invention is a tool-holder in which the angle of tilt is obtained by means of a set-of fourwedge shaped rings, two of which being made to rotate simultaneously with respect to the two others;

Furthermore, another object of the invention atool-holderin whichthe tool is mounted on a with asectionalong line 11-11 of Fig.1; 1'

.Fig. 3 is. a top view with a section along line IIIIII of Fig. 1. l I

Fig. 4 shows a second form of embodiment. Fig. 5 is another view of the second form of embodiment with partial section representedat alarger scale. p

Fig. 6 is a vpartial view of .athird form of embodiment. V v

Fig. 7 shows as'ection along line VII-VII. of Fig. 6; I v Fig. Sshows a detail of construction.

Fig. 9 is an end view. The tool-holder represented in Figs. 1 .to- .3 is

adapted particularly to the cutting of external threads. A circular forming tool I of a known type is securedon a holder 2. i .In view of obtaining a rigid connection between tool andholder,

the former is mounted on an axle v3. with aj conicalhead 4, a trued face. of the tool bearing against a trued lacev provided on the holder. Axle 3 trayerses said holder. .A conical hole 5 is equipped with a split conical sleeve 6 slipped over axle vEl, these parts being heldfirmly by a nut 8. The slopes ofthese cones being inverted, the clamping of the tool automatically-causes its centering.

Holder 2 has a stemlmade up of a conical portion .aanda IongercylindricaI portion I. Said stem is held in a clamping sleeve Ill witha square outer cross section or 0f other polygonal shape. Sleeve. I0 is bored outaxially from end toend with a conical seat]! tomatch said conical portion 9 of said stem. The latter is,,further equipped on its freeend emerging from sleeve ill with a screw thread 13 to cooperate with .a clamping. nut, l2. Sleeve II! has a longitudinal slot l4 parallel'to axis l5. This slot is traversed by a finger lfiengaging with a groove I! made in stem .1. 'This groove forming a smallangle with axis 15, may be, straight or aportionofasteep helix.

Finger 16 is providcdwith a shoulder l9 sliding in a groove cut in the edge of slot l4 and with. a square portion preventing rotation of said finger .around its. .axis.- On. said square portion. .is .mounted an index. plateZll running over a graduatedscale 2| located on one side of slot 14.

vv...Lastly, the outer end of finger l6 isprovided The.deviceejustdescribed may be used as follows;-

Said sleeve It] being meant to be clamped on the tool-carriage of the lathe (not shown) ,perpendicularly .to .theaxis .of-the latter, it. issunl- "cient ,to know the Tangle 'of .incline of the middle I helix pf' the thread-;with;respect1to a planepereach other.

pendicular to the axis of said helix. The forming tool is set by simply sliding said index 29 up to the desired division of scale 2|, graduated in degrees, corresponding to said angle. Tightening of the nuts 22 and I2 clamps the tool in its correct position in the tool-holder. The latter may be clamped then as a whole by any known means on the tool-carriage in the manner prescribed above to have the forming tool correctly positioned and fastened.

From the above, it may be observed that the angular setting of the tool in the tool-holder is an extremely easy and quick operation. It requires no fumbling, no trying, thereby allowing an important time saving.

As shown on the drawing, scale 2| may be preferably divided down to fractions of degrees and slot I1 is arranged so as to permit the tool to be inclined in one direction or the other with respect to the plane perpendicular to the axis of the screw depending on whether a right-hand or a left hand thread is to be cut.

The form of embodiment represented by Figs.

4 and 5 pertains particularly to the cutting of in- 29 thus formed takes up thethrust exerted by a bolt 31 screwed on the end of arbor 43, clamping a forming tool by its shoulder 40 and by the intermediary'of four wedge shaped rings 30, 35, 38 and 39 of equal taper, one face of each ring being square with its axis, the other face being oblique.

The extreme rings 30 and 38 are held angularly with respect to 43, i. e. with respect to stem by keys 32 and 32a respectively. They have their square face, with respect to the axis 34 of stem 25, directed against shoulder face 29 and bolt 31 respectively, their slanting face being parallel to The middle rings 35 and 39 have their oblique face 36 and 39a applied on oblique faces 33 and 38a of rings and 38 respectively.

A finger 44, secured in ring and engaging with r a radial groove 41 provided in ring 39, keeps these rings in a constant angular position one with respect to the other, their oblique face being parallel to each other, regardless of the angular displacement which may be imparted to ring 35 provided with radial sockets 51. Forming tool I has a sleeve 4| equipped with an internal shoulder serving for the clamping of the tool between said middle rings 35 and 39. Inner surfaces 45 and 46 of said inner rings 35 and 39 are rounded off so as to provide for the necessary clearance space for arbor 43. g

It may be seen readilythat, owing to this arrangement, the end faces of the ring pile always remain square with respect to the stem axis and that the total distance between faces 36 and 39a remains constant, regardless of the angular position given to adjusting ring 35, and that the axis of forming tool I may be brought to form an angle of tilt with the axis of stem 25 varying between 0 and twice the angle of taper common to all four wedge shaped rings.

This device functions as follows: The proper inclination of the forming tool with respect to axis 34, given by the diameter and 4 i pitch of the thread to be cut, is set by turning adjusting ring 35 by means of a rod or a key (not shown) engaging with sockets 51. When an index 48 provided on ring 35 (Fig. 4) matches with a division of a graduated scale 49 provided on ring 39 and corresponding to the prescribed angle, end bolt 31 is tightened. The tool-holder may then be clamped as a whole by any known means, with its axis 34 parallel with the axis of the thread to be cut, on the tool-carriage of the lathe not shown, split sleeve 26 affording very reliable clamping conditions.

Depending on whether a right handed or a left handed screw is to be obtained, finger 21 of sleeve 26 is engaged either with longitudinal groove 3|a or 3|b. It will be noted that due to the fact that the end faces of the ring pile remain parallel and perpendicular to axis 34, bolt 31 is subjected to traction alone.

This form of tool-holder for internal thread forming tools affords great advantages in that it permits the tool to be adjusted easily and rapidly in its angular position with respect to a plane perpendicular to the axis of the thread to be cut.

In the form of embodiment shown on Figs. 6' to 9 a forming tool I is secured to the end of a stem 25 of circular cross-section sliding in a longitudinally split clamping sleeve 26. Stem 25 is provided with two longitudinal and diametrically opposite grooves 3| (one of which alone being shown). With one of these grooves is engaged a finger 21 secured to clamping sleeve 26.

The end of stem 25, turned down to a smaller diameter, is equipped with an axle 5|, with its axis perpendicular to and crossing axis 50. On said axle 5| is mounted a tiltable head 52, carrying, rigidly clamped to its front face, a forming tool I. The resting surface of said head 52 is a portion of a sphere engaging with a spherical seat 53 provided in a ring 54. Said ring rests on a shoulder of stem 25 and is provided with a spherical spiral shaped groove 55. The protruding end of a finger 56 fastened and guided in a recess in said head cooperates with said groove.

A cylindrical ring 51, bearing an index 58 facing a graduated scale engraved on the lower edge of said ring 54, is slipped over stem 25 and prevented from rotating around same by a key 60.

Lastly, a knurled nut 6| screwed on a thread 62 cut in stem 25 allows said head to be clamped in the desired position.

The described device functions as follows:

Nut 6| having been loosened it is suflicient to cause ring 54 to rotate on stem 25. During this adjusting, spiral groove 55 guides finger 56 thereby causing head 52 to rock on its seat 53. The angle of tilt of head 52 varying in a continuous manner with the rotation of ring 54, it is possible to obtain a very precise angular setting of the angle of tilt of the forming tool with respect to axis 50.

Tightening nut 6| towards the tool end of the tool-holder causes axle 5| to clamp head 52 on its seat 53.

It is evident that in order to obtain a good performance of the described device it is necessary that the spiral groove be of the proper shape. The middle line of each section through a plane containing the axis must be tilted with respect to said axis by an amount equal to the angle of tilt to be obtained for the head when finger shall have its axis in said plane. In order to avoid inaccuracies of setting due to play between finger and guiding groove, it is of advantage to provide the end of the finger with a short cone as shown in Fig. 7 the shape of the guiding groove being then made to match.

It may be seen that in this latter form of construction the tool is made to rock around an axis whose position does not vary with respect to the stem of the tool-holder. This axis being perpendicular to that of the stem, it follows that the angle of inclination of the cutting edge of the forming tool does not vary during the setting of the aforesaid angle of tilt. This peculiarity has important advantages as it becomes unnecessary, as was the case with the device of Figs. 4 and 5, to verify the angular setting of the cutting edge for each modification of the angle of tilt of the tool, a tedious operation owing to the fact that during adjusting of the angle of tilt, the instantaneous axis of rotation varies and is diificult to locate.

It is evident that a tool-holder according to the invention may show different alternatives as to the details of construction as compared with the forms represented schematically and by way of examples on the annexed drawings. The essential feature is that said tool-holder is equipped with a device enabling the forming tool to be set and secured at the prescribed angle of tilt with respect to a plane perpendicular to the axis of the thread to be formed, with the assumption that said tool-holder is secured itself at a predetermined angle with respect to the axis of said thread.

The angle of tilt of the thread forming tool usually not exceeding a few degrees, it becomes possible, in order to allow for a precision setting, to provide the device with a widely spread graduation for the indication of said angle. In the forms of embodiment represented, the spreading of the scale has been made possible either by the use of a helical groove or inclined planes or a spherical spiral groove, but it is evident that any other known mechanically equivalent device may be used.

I claim:

1. A tool holder for a circular thread forming tool movable in a path parallel to the axis of they work piece to be threaded comprising an elongated substantially horizontal tool ,mount of polygonal cross section having a longitudinal bore, a rod axially slidably mounted therein, a shaft carried by one end of said rod perpendicular to the axis of said rod and substantially vertical, a headpivotally mounted on said shaft for rocking movement about the same, a circular thread forming tool carried by said head, a ring member rotatably mounted on said rod and provided with a spiral groove-in the end face thereof adjacent said head, a finger carried by said head and extending into said groove whereby rotary movement of the groove carrying ring about the rod will effect rocking movement of the head and thread cutting tool about said shaft.

2. A tool holder for a circular thread forming tool movable in a path parallel to the axis of the work piece to be threaded comprising an elongated substantially horizontal tool mount of polygonal cross section having a longitudinal head pivotally mounted on said shaft for rocking movement about the same, a circular thread forming tool carried by said head, a ring member rotatably mounted on said rod and provided with a spiral groove in the end face thereof adjacent said head, a finger carried by said head and extending into said groove whereby rotary movement of the groove carrying ring about the rod will effect rocking movement of the head and thread cutting tool about said shaft, said head having a rear portion of semi-spherical form and said ring having a semi-spherical socket formed in the grooved end face thereof to receive and cooperate with said head.

3. A tool holder for a circular thread forming tool movable in a path parallel to the axis of the work piece to be threaded comprising an elongated substantially horizontal tool mount of polygonal cross section having a longitudinal bore, a, rod axially slidably mounted therein, a shaft carried by one end of said rod perpendicular to the axis of said rod and substantially vertical, a head pivotally mounted on said shaft for rocking movement about the same, a circular thread forming tool carried by said head, a ring member rotatably mounted on said rod and provided with a spiral groove in the end face thereof adjacent said head, a finger carried by said head and extending into said groove whereby rotary movement of the groove carrying ring about the rod will effect rocking movement of the head and thread cutting tool about said shaft, said head having arear portion of semi-spherical form and said ring having a semi-spherical socket formed in the grooved end face thereof to receive and cooperate with said head, and a nut threaded on said rod and engaging the opposite end of said ring to press the latter against said head to retain the head in adjusted positions.

RENE ROSSETTI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 45,677 Rogers Dec. 27, 1864 292,316 Johnson Jan. 22, 1884 409,208 Landis Aug. 20, 1889 618,796 Kuhn Jan. 31, 1899 1,415,578 Knoop May 9, 1922 1,721,129 Mehl July 16, 1929 1,752,653 Ridler Apr. 1, 1930 1,880,742 Bosworth Oct. 4, 1932 1,880,878 Dickinson Oct. 4, 1932 2,447,094 Schlote -1 Aug. 17, 1948 2,458,753 Wallace Jan. 11, 1949 FOREIGN PATENTS Number Country Date 73,605 Switzerland Jan. 13, 1916 512,810 France ,Oct. 23, 1920 

